Set aside a budget of ~500 USD.
1. Identify source URLs where the contact info of Real Estate Builders & Developers sits.
2. Go to apifier.com
3. Hire them to crawl construction builder and real estate website developer URLs. You can grab the phone number and email address of many of them this way.
4. Use mailshake.com to do email blasts to these folks for biz dev.
5. Rinse and repeat for different geographies.